Strong permanent magnets are useful in manufacturing operations requiring reconfigurable holding and transporting devices for workpieces. For example, manufacturing facilities for high volume vehicle engine production require many pallets for moving engine components and assemblies between machining stations. Magnetic chucks can be used to reconfigure the pallets for different engines. Of course, chucks are also used for holding workpieces in a fixed position during machining. Compact permanent magnet chucks that can be conveniently turned on and off provide a means of providing reconfigurable fixtures for making different engines or other workpieces on the same manufacturing line.
The text and drawings of the specification of the parent application describe a very compact, efficient, and useful arrangement of permanent magnet plates and magnetically soft bodies for a magnetic chuck. The magnetic chuck has two substantially identical layers of an even number of alternating permanent magnet plates and interposed soft magnet bodies. The top surfaces of the two layers are sufficiently alike in the plan views of the permanent and soft magnet elements that one layer can be rotated through a small angle (usually no more than 90°, depending on the number of magnets) from an magnetically inactive position with like overlying shapes to an active position with like overlying shapes. In the active position of the chuck the magnetic field extends above the working face of the chuck and a strong attracting force is exerted on a ferromagnetic workpiece(s) to secure it against the chuck base or working surface.
A specific chuck or group of chucks must be designed to have a working face of specified shape and area and to exert a specified attractive force on a workpiece. It has been difficult to estimate the attractive force obtainable from a new design without building the chuck.
A commercial computer simulation software package for three-dimensional magnetostatics design is available. This software contains a CAD three-dimensional modeler, a material database, a Solver for computational algorithms of the magnetostatics field, and a graphical display capable of presenting the computational results in various parametric forms and solid modeling views. The primary goal of using such magnetostatics software is to shorten the time in the development and validation of any new magnetic chuck concept by not having to actually to build the unit. Still, it is found that the total time required in modeling the various sub-components and their engineering features in a proposed chuck design and in running the Solver to compute the expected magnetic attractive force takes one to three days. This invention provides a method for accurately estimating the strength of the magnetic attraction force given the magnetic properties of the permanent magnet plates and the soft magnet blocks, the clutch face area of the soft magnet blocks, and the contacting area of the sides of the interposed permanent magnet bodies that induce the magnetic field in the enclosing soft magnets.